1. Field of the Invention:
The present invention relates to a communication system. More particularly, the present invention relates to a method for requesting UpLink (UL) bandwidth allocation by a Mobile Station (MS), and allocating the uplink bandwidth by a Base Station (BS) in a communication system.
2. Description of the Related Art:
In a wireless communication system, there are a limited number of resources that can be used to support communication between users. For this reason, research is being actively conducted to find new or improved ways to ensure the efficient use of the limited resources. For efficient use of limited resources, it is necessary to prevent resources from being unnecessarily allocated, to rapidly collect allocated resources, and to re-allocate the collected resources for a different service.
When a bandwidth allocation is received from a Mobile Station (MS) through an uplink bandwidth allocation request, a Base Station (BS) should rapidly allocate the bandwidth. An uplink bandwidth allocation request is performed for each Connection IDentifier (CID) of an MS, and the bandwidth allocation by the BS is performed for each MS. That is, an MS requests allocation of a bandwidth required according to each CID, and a BS collects bandwidths requested according to each CID and allocates bandwidths according to each MS. A polling scheme, which is a representative scheme for requesting uplink bandwidth allocation by an MS, will now be described.
The polling scheme is used to request bandwidth allocation by transmitting a 6-byte bandwidth request header, in which information about an uplink bandwidth required for a corresponding CID is recorded, at a preset polling interval according to each CID of the MSs. The information about a bandwidth may be, for example, the amount of bandwidth. The polling scheme is used for service that requires bandwidths of various sizes during a certain interval, or for service that requires bandwidths of various sizes during various intervals.
FIG. 1 is a view illustrating the format of a conventional uplink bandwidth request header.
The uplink bandwidth request header includes a Header Type (HT) field 101, an EnCoding (EC) field 103, a type field 105, a Bandwidth Request (BR) field 107 and 109, a CID field 111 and 113, and a Header Check Sequence (HCS) field 115.
An MS can request bandwidth allocation by recording a CID, i.e. a Transport CID, which requests bandwidth allocation, in the CID field 111 and 113 of the uplink bandwidth request header shown in FIG. 1, and then transmits the uplink bandwidth request header to a BS. The Transport CID is allocated in one-to-one correspondence with a service flow of the BS, which manages the MS, and the Transport CID is unique only to the BS.
Due to the characteristic of the Transport CID which is unique only to the BS, when the MS moves from a coverage area of a BS (e.g. a serving BS), which is currently managing the MS, to a coverage area of a BS (e.g. a target BS) other than the serving BS, through a handover or the like, the Transport CID of the MS collides with a Transport CID allocated to MSs in the area covered by the target BS. In order to avoid such a collision, when an MS moves into the coverage area of the target BS, the target BS performs a separate CID update operation to allocate a new Transport CID to the MS.
As described above, since the Transport CID is unique only to a corresponding BS, when an MS having a Transport CID is handed over from the current serving BS to a target BS, the target BS must perform a CID update operation for the MS. Therefore, there is a problem in that resources are wasted due to a CID update that must be performed whenever a handover is performed.